An induction or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor therefore does not require mechanical commutation, separate-excitation or self-excitation with respect to transfer of energy from stator to rotor, and is thus quite different from universal, DC and large synchronous motors. Thus, the induction motor's essential operating characteristic is that rotation is created solely by induction instead of through use of separate winding excitation (as in synchronous or DC machines) or through self-magnetization (as in permanent magnet motors).
Induction motors are commonly used in many industrial and commercial applications. Such motors have well known advantages including low production cost, easy operation, easy maintenance and relatively good efficiency.
Techniques for controlling the speed of induction motors are well known in the art. With the advent of semiconductor power electronics and control circuits, it has become much easier to exercise motor control. However, there continues to be a need for improved driver systems for use with induction motors, and there is also a need for a single driver system solution compatible with both single-phase and three-phase induction motors.